It is known that battery life for a WTRU is an important aspect of the quality of service that an end user perceives, and any measure that could achieve battery savings is a desirable accomplishment in wireless communication system design. Some of the existing systems and methods for conserving battery power relate to reducing the power of at least part of the WTRU to conserve battery life. For example, in U.S. Pat. No. 5,539,925, a base station sends a signal to a mobile station to turn off the mobile station for a length of time communicated in the message. At the end of the “off” period, the mobile station will automatically restart itself to determine whether it needs to remain active or whether it can be turned off for an additional period.
U.S. Pat. No. 6,463,042 relates to a method in which a wireless terminal receives a header packet and estimates the power level of the header packet. The wireless terminal then receives a portion of a following data packet, and estimates the power level of the data packet. A comparison is made between the power level of the header packet and the power level of the data packet. If the power levels are approximately equal, then the wireless terminal will receive and process the remainder of the data packet. If the power level of the header packet is greater than the power level of the data packet, then this is an indication that the base station is operating in quasi-discontinuous transmission (Q-DTX) mode and that the wireless terminal can ignore the remainder of the data packet and put some of the components into a low power mode.
In U.S. Pat. No. 6,463,307, a hibernation request is made by either the base station or the mobile terminal. Parameters relating to the hibernation period, including when to wake the mobile terminal to check for paging messages or whether the mobile terminal has a data packet to send, are then set by the base station and transmitted to the mobile terminal. Once the hibernating period has ended, if there are any waiting paging messages, the mobile terminal is awakened and the paging messages are checked. If there are no paging messages, then a determination is made whether the mobile terminal has any pending data packets to send. If there are pending data packets, then the mobile terminal is awakened and the packets are sent. If there are no pending packets, then the mobile terminal returns to the hibernation mode.
The systems and methods described above relate only to the powering-down of components to conserve battery power, and not to methods for conserving battery power while the WTRU is actively transmitting. It would, therefore, be desirable to achieve battery savings when the WTRU is active.